1. Technical Field
This invention relates to the area of automated mail processing and more particularly to the use of optical character recognition and knowledge base systems methods in mail processing to effect correction of optical recognition errors, aid an operator in disambiguating address misreads, and validating the correctness of the address down to the delivery sequence.
2. Background Art
In the United States in 1988 approximately 160 billion pieces of mail were delivered by the United States Postal Service. The volume of mail is growing at a compound rate of approximately 5% a year. To handle such massive volume of mail, several methods utilizing automated means have been experimented with and installed on a limited operational basis. One means of automated mail processing utilized today revolves around optical character recognition (OCR). The OCR is capable of scanning the address area on an envelope and interpreting it into machine-readable alphabetic and numeric characters. State of the art optical character recognition is restricted to machine printed addresses and is unusable for handwritten or handprinted characters. Additionally, OCR is prone to misread characters and on occasion has difficulty in discerning lines in the address block and, when there is interference on the face of the envelope, is unable to find the address box. When a misread occurs, the mail piece cannot be properly sorted and either is rejected or an attempt is made to enter the correct address read by utilizing the directory of the street or city names. Since most mail reading OCRs process mail pieces at the rate of 600 to 800 per minute, the amount of time in which misread correction can be performed limits the correction to only the most superficial errors and does not allow for validation of the OCR read of the address using all constituent information in the address box. For example, no attempt is made to determine that a given street actually exists within a certain zip code and that the city/state match the zip code and above all that the addressee actually exists at this location. The inability to do complete validation and verification on the OCR scan has limited the utility of OCRs to mainly reading the outgoing city/state/country/destination which is normally found on the bottom most line of the address box. The other lines of the address, which can number an additional five lines and the information to sort a letter down to delivery sequence within a building, cannot at this time be scanned, OCRed, validated and used for sortation down to delivery sequences.
Without the ability to validate the correctness of the OCR interpretation of all lines in the address block, the reliability of sortation down to delivery sequence drops dramatically. This leads to the situation where a major part displaceable cost in the mail sortation process results in the handling of mail after it arrives at its destination post office, whereas the reliability of OCR at that point drops dramatically to approximately 25% reliability.
An alternative to the use of OCRs is the preprinting of envelopes with a bar code of phosphorescent ink encoding that allows machines to simply and accurately read address information off the envelope without having to do optical character recognition. The methods related to pre-printing envelopes however, fall short since they are only a relatively small fraction of the mail volume and hence from a logistics standpoint only provide useful sortation to the destination post office and cannot substantiate a large enough volume of mail to make it worthwhile to process the mail automatically down to the delivery sequence.
The invention disclosed herein addresses the problem of performing with reliability, mechanical separation of mail down to the "delivery sequence" utilizing optical character recognition and image scanning techniques coupled with knowledge based operator-assisted disambiguation and validation of the address data down to the delivery sequence. The invention also includes a method to do this off-line to re-associate the sortation information with the mail piece and optimize mail processing by utilizing apriori knowledge of the mail distribution.